Speaking of one syllable names...
One of my good friends is named Eva and her middle name is Mae. I think Eva Mae/May is a lovely combo.
Also, perhaps:
Eva Jane
Eva Grace
Eva Joy
Eva Lynn
Eva Leigh
Eva Ruth
Eva Dawn
Eva Bree
Eva Paige
Eva Fern
Eva Brynn
Eva Quinn
Eva Joan
Eva Wren
and for multi-syllable suggestions:
Eva Olivia
Eva Serena
Eva Meredith
Eva Fiona
Eva Renee
Eva Ariella